This invention relates to a seat recliner mechanism and, more particularly, to a motor vehicle seat recliner mechanism which permits the seat back angle relative to the seat bottom to be varied as desired by the seat occupant.
Many motor vehicles now feature seat recliner mechanisms which provide added comfort and convenience for vehicle occupants. Numerous types of seat recliner mechanisms are known to the prior art. For example, U.S. Pat. No. 4,372,610, issued to A. J. Fisher III et al on Feb. 8, 1983, describes a recliner mechanism employing a pair of meshing straight toothed racks. One of the racks is connected to the upper recliner structure through a quadrant component. Adjustment of the seat reclined angular position is accomplished by changing the meshed position of one rack with respect to the other. Patent application Ser. Nos. 589,229 filed Mar. 14, 1984, and 594,742 filed Mar. 29, 1984, each assigned to the assignee of this application, relate to improvements in such recliner mechanisms. Patent application Ser. Nos. 602,370 filed Apr. 20, 1984, and 632,597 filed July 19, 1984, also assigned to the assignee of this application, relate to recliner mechanisms employing rotating gears for seat recliner position adjustment.
Although devices in accordance with the above-entitled patents and applications perform satisfactorily, it is desirable to provide further improvements in the design of seat recliner mechanisms. Many of the currently known seat recliner mechanism designs employ meshing teeth for position fixing which provide stepped changes in adjusted angular position. It is therefore desirable to provide an improved seat recliner mechanism featuring continuously variable adjusted seat back angular positions so that the user is not constrained to fixed angular positions dictated by the recliner mechanism. Many currently known seat recliner mechanisms further produce annoying clattering or "ratcheting" sounds during adjustment. It is therefore desirable to provide a seat recliner mechanism which provides silent operation and has smooth release characteristics. Another desirable characteristic for a motor vehicle seat recliner is the ability to prevent unrestrained pivoting motion of the seat back in the event of failure or improper operation of the seat recliner mechanism. Designers are further constantly striving for ease of production, low cost, simplicity, and reliability of motor vehicle hardware components.
The above described features for a motor vehicle seat recliner mechanism are provided in accordance with this invention by employing such a mechanism having a gear transmission coupled to a spring clutch actuator mechanism which fixes the angular position of the seat back. In a preferred embodiment of this invention, a curved toothed rack is provided on a component which rotates with the upper recliner mechanism and meshes with a gear which is rotatable within the lower recliner mechanism. One or more additional gears are employed to rotatably drive a drum. Fixing of the seat reclined position is achieved by providing a coil spring clutch which wraps around the drum. An actuation mechanism is employed to selectively tighten or loosen the coil spring clutch around the drum to either restrain or permit drum rotation. The recliner mechanism according to this invention further includes a redundant positioning pawl which acts in conjunction with the coil spring actuator to restrain pivotable motion of the upper recliner structure. This redundant positioning pawl prevents unrestrained motion of the seat back in the event of failure or improper operation of the spring clutch actuator.
The recliner mechanism according to this invention is usable for motor vehicle seats which are installed in two or four door type cars, as well as for other types of motor vehicles. In four door car models, the front seat back typically does not need to be folded forward to permit access to the rear seat occupant area. However, for two door designs having a rear seat occupant area, such provisions are usually necessary. Therefore, this invention is described in conjunction with an inertia sensitive seat back locking device according to prior art designs which normally permits the front seat back to be folded forward but acts to prevent folding when the vehicle is subjected to deceleration above a predetermined level. The inertia sensitive seat back locking system described in conjunction with this invention and various similar devices are detailed by several of the previously mentioned U.S. patents and applications.